Conventional photographic packets for day light loading generally leak some degree of light into a light shielding envelope enclosing photosensitive film material. Light leakage is objectionable because it may cause damage to the photosensitive film material in the assemblage and, therefore, render the film unusable. Typically, in photographic packets P' (FIGS. 1-2), a clip or transversely disposed element K that closes an open end (trailing end section) of a light shielding envelope E enclosing the film is configured such that when the trailing end section of the envelope E' is fully inserted in the clip C, a "gap" G exists between the clip C and the trailing end portion of the envelope. This "gap" G (shown clearly in FIG. 2) provides a passageway for some amount of light to enter the envelope (E) thereby jeopardizing the light integrity of the assemblage. Although the prior art "clip" uses "staking" along a transverse edge to secure a film carrier sheet, there is no provision for eliminating the "gap" as a potential source of light leakage into the light shielding envelope. Moreover, the prior art film packets do not provide additional means for fully utilizing the "clip" or similar member for virtually eliminating the ingress of light into the closable end of the light shielding envelope.
The prior art is replete with film assemblages of the type referred to above. Examples may be found in the following documents:
U.S. Pat. No. 818,543--Discloses a photographic holder (g) in use with an assemblage comprising a film sheet (a) mounted on a carrier (b) and light-tightly enclosed by a withdrawable envelope (f); the assemblage has a manually graspable end portion extending outside the holder, where a medial part, but not the two lateral parts, of the enclosed carrier end is cut back to permit (by selective grasping) withdrawal of either the envelope alone or the whole assemblage.
U.S. Pat. No. 3,586,501--Discloses a self-processable film assemblage (10) in use with a film holder (32), the assemblage comprising a photosensitive film sheet (26) having at one end a transversely disposed "clip" (20) for closing a mating open end (12a) of a light-excluding envelope (12) telescopically received over the film sheet, the clip being adapted for selective engagement and disengagement by a latch (42) in the holder to prevent and permit, respectively, film sheet movement with the envelope when an externally accessible closed end (12b) thereof is pulled away from the holder, the closed end (12b) terminating in a pair of laterally offset graspable tabs (22,24) extending respectively from opposing walls (14,16) of the envelope, the film sheet (26) having a leader (50) extending therefrom toward the envelope closed end (12b) with a recessed end portion (50a) provided to allow only the envelope to be grasped and pulled from the holder, the envelope also having a stop-strip (46) transversely disposed thereon near its open end (12a) and engageable by another latch (48) in the holder to limit outward movement of the envelope.
International Patent Publication No. WO 87/10469--Discloses a photographic film holder (47), the assemblage comprising a carrier (1) having twin film sheets (2) removably mounted on opposite faces of a film-carrying region (3) thereof, with an elongate, narrow tab portion (6) extending longitudinally from one end of the film-carrying region and a rigid, light-sealing "clip" (8) disposed transversely over both carrier faces at the opposite end, together with a light-excluding envelope (14) having an open end (15) that is telescopically slidable over the carrier and film sheets into light-sealing engagement with the clip and a closed end (20) that both conformably encloses and extends beyond the carrier tab portion (6), so that (by selective grasping) either the envelope alone may be pulled away from the carrier and film sheets or the whole assemblage may be pulled together, the clip (8) being engageable by a cooperating tab (43) in the holder to prevent the carrier and film sheets from moving when only the envelope is to be withdrawn, the envelope also having a pair of stops-trips (14a) disposed transversely on both walls thereof near its open end (15), and engageable with a cooperating stop (43a) in the holder, to limit the extend of envelope withdrawal when either film sheet is to be exposed.
U.S. Pat. No. 4,821,054--Discloses a photographic film assemblage that has film carrier having an asymmetrical tab bearing adhesive material and , at an opposite end, a transverse light locking element. Telescopically receivable over the carrier and film is a light shielding envelope. The envelope has an closable end that is closed with the light locking element.
While such film packets may have proven useful for their respective purposes, there has remained a need for an improved film packet so constructed and configured that a film sheet therein cannot inadvertently be exposed by unintended relative movement between its light-excluding parts, especially during handling and transport of the film packet either before or after intended exposure in associated photographic apparatus.